Rip saws are customarily provided with powered feed rollers to drive timber workpieces along a fence and past a band saw blade. The positions of the feed rollers and fence relative to the blade are each adjustable by means of a handwheel and screw. The feed rollers are biassed towards the fence by means of a spring or weights or hydraulically. This allows a certain amount of variation, perhaps 25 mm in the width of the workpiece fed. The problem is to allow a greater variation in the width of the workpiece without the need to reposition the feed mechanism. A workpiece may be put through a machine a number of times, and reduced in width at each pass. The invention reduces the frequency at which it is necessary to adjust the position of the feed mechanism.